Lesson Eighteen Marine engines Marine engine is an engine that propels a water-born vessel. Even in small craft the marine engine must have the following characteristics: reliability, light weight, compactness, fuel economy, low maintenance, long life, relative simplicity for operating personnel, ability to reverse, and ability to operate steadily at low or cruising speed. The relative importance of these characteristics varies with the service performed by the vessel, but reliability is of prime importance. Steam engines Steam, used to drive the earliest powered vessels, is still a common type of propulsion for large ships. The diesel engine has gained wide acceptance in foreign merchant ships, but in the United States, the majority of seagoing vessels use steam propulsion Reciprocating steam engines Early engines commonly used steam flowing in series through as many as four cylinders whose pistons had the same stroke but were of increasing diameters. This system provided for an expansion or increase in steam volume which accompanied the decrease in pressure to the exhaust under a vacuum. The modern, multicylinder, uniflow marine steam engine, with complete expansion in each cylinder, shows better steam economy. Because it has the same diameter for all cylinders( two to six in number ) it is preferable from a manufacturing viewpoint. Equal power is developed by each cylinder; units of four cylinders or more have good torque and balance characteristics. A steam rate of 10 lb/hp/hr(1.7 kg/M) with 275 psi(1.90 Mpa)at 240@F (116C) super heat is attainted. Uniflow engines as large as 5000 hp(3. 7MW) have been used on shipboard. Normally, steam engines are double-acting; that is, steam acts on each side of the pistons. With superheated steam, piston-cylinder lubrication must be provided. Pure feed-water is required by modern, high-capacity boilers; thus, an effective oil filter is installed where the condensate must be returned to the boiler Steam turbines The marine steam turbine has the advantages of direct rotary motion little or no rubbing contact of pressure-confining surfaces, and ability to use effectively both highly super heated steam and steam at low pressure, that is, at a high vacuum where specific volumes of over 400 ft/b are reached For good efficiency of steam turbines, high rotative speeds are required. This requirement led to the introduction of the reduction geared turbine and turboelectric drive. These system give efficient turbine speeds and efficient propeller rmp. With geared turbine, for example, turbine rotor speeds range from 3000 to 10,000 rm while propeller rmp is reduced to the 80 to 400 range Steam is generally supplied to the turbine at 850 psi(5.9MPa) and 950 F(510 C) by pair of oilfired marine water-tube boiler, and the exhaust from the turbine is usually at 1. 5 in. lig(5. IkPa)absolute. Forced draft fans and other auxiliaries are usually motor-driven, except for the main feed pimps which are usually driven by an auxiliary urbine. Electric power is provided by a separate turbogenerator In low-powered geared turbines, steam completes its expansion in one rotor and casing. Such a design has been used in geared turbines of up to 8000 shaft horsepower(ship) or a shaft power of 6 Mw. However, series flow through two or even three casings is preferable in most steam turbines. This arrangement provides more flexibility in turbine design, allowing for different and optimum revolutions for high-and low-pressure rotors. Also, in a seagoing vessel in case of casualty to one turbine or its high-speed pinion, the vessel usually can make port with the remaining turbine in operation A steam turbine is made up of fixed blades, usually called nazzles, and rotating blades. A stage is generally one stationary row and one moving row. Impulse staging has all the steam pressure drop taking place in the fixed blades. The moving row then absorbs the kinetic energy produced. Reaction staging results when some of the assume drop occurs in the moving blades, the degree of reaction depending on the design Modern marine practice favors impulse staging in the high-pressure end of the turbine because of the steam progresses toward the low-pressure end where the value is much greater the reaction stage is more efficient. The arrangement has a cross compound system with a high-pressure unit of 7 to 10stages and a low-pressure unit of 6to 8 stages, each driving a pinion of a reduction gear
Lesson Eighteen Marine Engines Marine engine is an engine that propels a water-born vessel. Even in small craft the marine engine must have the following characteristics: reliability, light weight, compactness, fuel economy, low maintenance, long life, relative simplicity for operating personnel, ability to reverse, and ability to operate steadily at low or cruising speed. The relative importance of these characteristics varies with the service performed by the vessel, but reliability is of prime importance. Steam engines Steam, used to drive the earliest powered vessels, is still a common type of propulsion for large ships. The diesel engine has gained wide acceptance in foreign merchant ships, but in the United States, the majority of seagoing vessels use steam propulsion. Reciprocating steam engines Early engines commonly used steam flowing in series through as many as four cylinders whose pistons had the same stroke but were of increasing diameters. This system provided for an expansion or increase in steam volume which accompanied the decrease in pressure to the exhaust under a vacuum. The modern, multicylinder, uniflow marine steam engine, with complete expansion in each cylinder, shows better steam economy. Because it has the same diameter for all cylinders (two to six in number), it is preferable from a manufacturing viewpoint. Equal power is developed by each cylinder; units of four cylinders or more have good torque and balance characteristics. A steam rate of 10 lb/hp/hr (1.7 kg/MJ) with 275 psi (1.90 Mpa) at 240°F （116°C）super heat is attainted. Uniflow engines as large as 5000 hp (3.7MW) have been used on shipboard. Normally, steam engines are double-acting; that is, steam acts on each side of the pistons. With superheated steam, piston-cylinder lubrication must be provided. Pure feed-water is required by modern, high-capacity boilers; thus, an effective oil filter is installed where the condensate must be returned to the boiler. Steam turbines The marine steam turbine has the advantages of direct rotary motion, little or no rubbing contact of pressure-confining surfaces, and ability to use effectively both highly super heated steam and steam at low pressure, that is, at a high vacuum where specific volumes of over 400 ft3 /lb are reached. For good efficiency of steam turbines, high rotative speeds are required. This requirement led to the introduction of the reduction geared turbine and turboelectric drive. These system give efficient turbine speeds and efficient propeller rmp. With geared turbine, for example, turbine rotor speeds range from 3000 to 10,000 rmp, while propeller rmp is reduced to the 80 to 400 range. Steam is generally supplied to the turbine at 850 psi (5.9MPa) and 950°F (510°C) by pair of oilfired marine water-tube boiler, and the exhaust from the turbine is usually at 1.5 in. lig(5.1kPa) absolute. Forced draft fans and other auxiliaries are usually motor-driven, except for the main feed pimps which are usually driven by an auxiliary turbine. Electric power is provided by a separate turbogenerator. In low-powered geared turbines, steam completes its expansion in one rotor and casing. Such a design has been used in geared turbines of up to 8000 shaft horsepower (ship) or a shaft power of 6 MW. However, series flow through two or even three casings is preferable in most steam turbines. This arrangement provides more flexibility in turbine design, allowing for different and optimum revolutions for high-and low-pressure rotors. Also, in a seagoing vessel in case of casualty to one turbine or its high-speed pinion, the vessel usually can make port with the remaining turbine in operation. A steam turbine is made up of fixed blades, usually called nazzles, and rotating blades. A stage is generally one stationary row and one moving row. Impulse staging has all the steam pressure drop taking place in the fixed blades. The moving row then absorbs the kinetic energy produced. Reaction staging results when some of the assume drop occurs in the moving blades, the degree of reaction depending on the design. Modern marine practice favors impulse staging in the high-pressure end of the turbine because of the steam progresses toward the low-pressure end where the value is much greater the reaction stage is more efficient. The arrangement has a cross compound system with a high-pressure unit of 7 to 10stages and a low-pressure unit of 6to 8 stages, each driving a pinion of a reduction gear
a turbine is capable of operation in only one direction. In order to provide reverse power, a second turbine is installed on the shaft of the low-pressure ahead turbine. The astern turbine is usually not more than three moving rows of blades, but it may be only two. It produces about 40% of the normal ahead horsepower. Since this unit is urning backward in normal ahead operation, it is located in the low-pressure end of the low-pressure turbine. The steam at this point has a very low density, and hence the astern turbine has a low windage loss The propeller is reversed by closing the steam value to the ahead turbine and opening the value to the astern urbine Gas turbine The gas turbine is a relative newcomer to the marine field. It generally considered of an axial compressor discharging compressed air to a combustion chamber where fuel is burned, adding heat. The produces of combustion at high temperature and pressure then pass through a gas turbine that drives the compressor and load. Generally, the term"gas turbine "is applied to the entire plant. If lower pressure ratios (final pressure leaving the compressor divided by initial pressure entering) are used, a large amount of heat is available in the exhaust gas which may be recovered by heating the compressed air before it enters the combustion chamber. This is done in a regenerator. With higher pressure ratios the expansion through the turbine is so great that the exhaust gas temperature is insufficient to heat the compressed air Two distinct types of gas turbines are appearing in the marine field the aircraft-derived type and the industrial type. The aircraft-derived type uses a jet engine as a gas generator, which discharges to a gas turbine driving the load. This type of plant offers simplicity and light weight but must burn high-quality fuel. The industrial gas turbine is a more rugged machine designed for long life and is capable of using low grades of fuel properly washed. This plant usually uses a regenerator. The gas turbine offers simplicity, ease of control, and efficiency, but requires special fuel or special treatment of the fuel Large amounts of air and exhaust gas are used and as a result uptakes and air supply are a special problem. The aircraft-derived gas turbine seems destined to drive a large number of naval combatant ships. Selections of this type for a new class of naval destroyers has been announced. The industrial type will be used for merchant vessels where its greater weight will be of little disadvantage Both diesel and gasoline internal combustion engines are used in marine applications. Many moderate and lowpower marine installations use automotive or locomotive engines designed for variable load and intermittent service. High-power marine propulsion units normally are called on to operate continuously under load. Therefore, the brake horsepower(bhp)rating of units selected for marine service should be conservative The gasoline engine is the most common power plant for pleasure craft. It is inexpensive to buy and maintain Because of its widespread use in automobiles, most parts are readily available. In most areas gasoline costs slightly more than diesel fuel, but the cost differential is usually insufficient to make up the difference between the cost of gasoline and diesel engines. Gasoline presents an explosion and fire hazard, which is its major Direct-drive diesels For typical commercial freight vessels, direct-drive diesels provide economical service. For good propeller efficiency, the propeller rpm should be under 120+. Such a top limit on engine revolutions results in a large, heavy, bulky, slow-rpm engine. However, the direct-drive diesels have a lower fuel oil consumption than do higher-rpm units, and with suitable fuel treatment they will operate on the better grades of the cheaper fuel oil burned in boilers Slow-speed, direct-drive diesels are favored by many European owners and shipbuilders. Turbo-charged, two-cycle, single-acting diesel engines of 50 000 bhp(37MW of brake power) are now available; such engines weigh more than 100 lb/bhp(60kg/kw of brake power). For high horsepower the total machinery weight fo diesels is more than the weight of geared turbine machinery, including boilers and auxiliaries Moderate-speed diesels Diesel engines of 250-500 rpm are available in two and four cycle, single-acting types, generally with trunk pistons. In some marine applications they are connected directly to the propeller and thus fitted only with reverse gear. However, they are also employed with geared diesel and diesel-electric drive
A turbine is capable of operation in only one direction. In order to provide reverse power, a second turbine is installed on the shaft of the low-pressure ahead turbine. The astern turbine is usually not more than three moving rows of blades, but it may be only two. It produces about 40% of the normal ahead horsepower. Since this unit is turning backward in normal ahead operation, it is located in the low-pressure end of the low-pressure turbine. The steam at this point has a very low density, and hence the astern turbine has a low windage loss. The propeller is reversed by closing the steam value to the ahead turbine and opening the value to the astern turbine. Gas turbine The gas turbine is a relative newcomer to the marine field. It generally considered of an axial compressor discharging compressed air to a combustion chamber where fuel is burned, adding heat. The produces of combustion at high temperature and pressure then pass through a gas turbine that drives the compressor and load. Generally, the term “gas turbine” is applied to the entire plant. If lower pressure ratios (final pressure leaving the compressor divided by initial pressure entering) are used, a large amount of heat is available in the exhaust gas which may be recovered by heating the compressed air before it enters the combustion chamber. This is done in a regenerator. With higher pressure ratios the expansion through the turbine is so great that the exhaust gas temperature is insufficient to heat the compressed air. Two distinct types of gas turbines are appearing in the marine field: the aircraft-derived type and the industrial type. The aircraft-derived type uses a jet engine as a gas generator, which discharges to a gas turbine driving the load. This type of plant offers simplicity and light weight but must burn high-quality fuel. The industrial gas turbine is a more rugged machine designed for long life and is capable of using low grades of fuel, properly washed. This plant usually uses a regenerator. The gas turbine offers simplicity, ease of control, and efficiency, but requires special fuel or special treatment of the fuel .Large amounts of air and exhaust gas are used, and as a result uptakes and air supply are a special problem. The aircraft-derived gas turbine seems destined to drive a large number of naval combatant ships. Selections of this type for a new class of naval destroyers has been announced. The industrial type will be used for merchant vessels where its greater weight will be of little disadvantage. Internal combustion engines Both diesel and gasoline internal combustion engines are used in marine applications. Many moderate and lowpower marine installations use automotive or locomotive engines designed for variable load and intermittent service. High-power marine propulsion units normally are called on to operate continuously under load. Therefore, the brake horsepower (bhp) rating of units selected for marine service should be conservative. The gasoline engine is the most common power plant for pleasure craft. It is inexpensive to buy and maintain. Because of its widespread use in automobiles, most parts are readily available. In most areas gasoline costs slightly more than diesel fuel, but the cost differential is usually insufficient to make up the difference between the cost of gasoline and diesel engines. Gasoline presents an explosion and fire hazard, which is its major disadvantage. Direct-drive diesels For typical commercial freight vessels, direct-drive diesels provide economical service. For good propeller efficiency, the propeller rpm should be under 120±. Such a top limit on engine revolutions results in a large, heavy, bulky, slow-rpm engine. However, the direct-drive diesels have a lower fuel oil consumption than do higher-rpm units, and with suitable fuel treatment they will operate on the better grades of the cheaper fuel oil burned in boilers. Slow-speed, direct-drive diesels are favored by many European owners and shipbuilders. Turbo-charged, two-cycle, single-acting diesel engines of 50 000 bhp (37MW of brake power) are now available; such engines weigh more than 100 lb/bhp (60kg/kw of brake power). For high horsepower the total machinery weight for diesels is more than the weight of geared turbine machinery, including boilers and auxiliaries. Moderate-speed diesels Diesel engines of 250-500 rpm are available in two and four cycle, single-acting types, generally with trunk pistons. In some marine applications they are connected directly to the propeller and thus fitted only with reverse gear. However, they are also employed with geared diesel and diesel-electric drive
The weight of such engines runs about 35-70 Ib/bhp(21-43 kg/kw of brake power High-speed diesels Many high-speed diesel engines of 600 rpm and more(some types originally developed for truck and locomotive service )are available for marine propulsion. Opposed piston types have been developed; other manufacturers favor a v type to reduce weight. Such engines are of two-and four-cycle types and usually weigh 10-40 lb/bhp(6-24kg/kw of brake power ) Because of less efficient scavenging, breaker power, and other factors, their fuel and lubricating oil rates are higher than for large, low-speed diesels Except for direct drive in moderate or fairly high-speed craft, marine applications of diesel engines or with diesel-electric drive to provide good propeller efficiency. Because their pistons, valves, and other components are small, standardized, and carried in stock, repairs are readily made, with the result that engines of this type are popular for no Oil consumption and starting Lubricating oil consumption of diesel engines is high because of the cylinder-piston lubrication that must be provided and the contamination of the crankcase oil with residues blown by the piston rings. In large engines this contamination is avoided by using piston rod-crosshead construction so that the crankshaft, connecting rods, and crossheads operate in a closed casing separated from the working cylinder. These engines are started and maneuvered by pressure from one or more reservoirs filled with air at about 250 psi(1.7 MPa). To make it feasible to start and readily reverse, two-cycle, single-acting marine engines should have at least four cylinders; four-cycle engines should have five or more cylinders Nuclear power Very successful installations of nuclear power have been made in submarines and a few surface ships Operation of the first nuclear merchant ship, the Savannah, was successful technically but not commercially. (The operating crew required special training, and it would be difficult to replace with only one commercial nuclear ship in service.) Mechanical reduction gears Reduction gearing for diesel and gasoline engines allows the use of a relatively high engine speed and lower more efficient propeller speed. Speed reduction ratios of 1.8: 1 to 4: 1 are common, preferably with helical teeth to give better wear and quieter performance. A reverse gear device often is incorporated in lowpower gears for astern operation. Other methods for providing reverse rotation use a direct reversing engine or a controllable-pitch propeller One, two, three, or four engines may drive the same gear through individual pinions. The use of a friction, electromagnetic, pneumatic, or hydraulic coupling serves to disconnect any engine. By reversing one or more engines, ready maneuvering, including astern operation, is provided for by the use of the respective coupling The high rpm(3000-9000) of modern marine steam turbine and the low revolutions of an effective propeller (as low as 80 rpm) require the use of two-stage gearing. Gear teeth of harder material than the gear. The gear trains are of the double helical, type to avoid heavy axial thrust. Double reduction gears are constructed with flexible couplings between the high-speed train and the low-speed elements Mechanical reduction gears are carefully constructed to close tolerances. They have forced lubrication in sprays ahead of the meshing teeth, to the bearings, and to the flexible couplings. Tests have shown that bearings represent at least half the power loss of the entire gear set Turboelectric drive This type of drive, comprising one or more steam turbine generators and ac propulsion motors, is al for ship propulsion. It was installed in many United States tankers during World War Il because of ava manufacturing facilities. The synchronous motors are provided with an induction winding for starting and reversing. Relatively large changes in propeller revolutions are made by alteration of the turbogenerator speed Motor, generator, exciter, and cooling equipment losses result in several percent lower efficiency than with geared steam turbines. Weights and costs are generally 25-30% higher than for the comparable turbine gear arrangement. Electric drive is not employed unless it offers significant operational or design advantages. These include flexibility of control and the independence of the location of the turbo generator relative to the propeller shaft or propulsion motor
The weight of such engines runs about 35-70 lb/bhp (21-43 kg/kw of brake power). High-speed diesels Many high-speed diesel engines of 600 rpm and more (some types originally developed for truck and locomotive service ) are available for marine propulsion. Opposed piston types have been developed; other manufacturers favor a V type to reduce weight. Such engines are of two-and four-cycle types and usually weigh 10-40 lb/bhp (6-24kg/kw of brake power). Because of less efficient scavenging, breaker power, and other factors, their fuel and lubricating oil rates are higher than for large, low-speed diesels. Except for direct drive in moderate or fairly high-speed craft, marine applications of diesel engines or with diesel-electric drive to provide good propeller efficiency. Because their pistons, valves, and other components are small, standardized, and carried in stock, repairs are readily made, with the result that engines of this type are popular for nonoceangoing services. Oil consumption and starting Lubricating oil consumption of diesel engines is high because of the cylinder-piston lubrication that must be provided and the contamination of the crankcase oil with residues blown by the piston rings. In large engines this contamination is avoided by using piston rod-crosshead construction so that the crankshaft, connecting rods, and crossheads operate in a closed casing separated from the working cylinder. These engines are started and maneuvered by pressure from one or more reservoirs filled with air at about 250 psi (1.7 MPa). To make it feasible to start and readily reverse, two-cycle, single-acting marine engines should have at least four cylinders; four-cycle engines should have five or more cylinders. Nuclear power Very successful installations of nuclear power have been made in submarines and a few surface ships. Operation of the first nuclear merchant ship, the Savannah, was successful technically but not commercially. (The operating crew required special training, and it would be difficult to replace with only one commercial nuclear ship in service.) Mechanical reduction gears Reduction gearing for diesel and gasoline engines allows the use of a relatively high engine speed and lower, more efficient propeller speed. Speed reduction ratios of 1.8:1 to 4:1 are common, preferably with helical teeth to give better wear and quieter performance. A reverse gear device often is incorporated in lowpower gears for astern operation. Other methods for providing reverse rotation use a direct reversing engine or a controllable-pitch propeller. One, two, three, or four engines may drive the same gear through individual pinions. The use of a friction, electromagnetic, pneumatic, or hydraulic coupling serves to disconnect any engine. By reversing one or more engines, ready maneuvering, including astern operation, is provided for by the use of the respective coupling. The high rpm (3000-9000) of modern marine steam turbine and the low revolutions of an effective propeller (as low as 80 rpm) require the use of two-stage gearing. Gear teeth of harder material than the gear. The gear trains are of the double helical, type to avoid heavy axial thrust. Double reduction gears are constructed with flexible couplings between the high-speed train and the low-speed elements. Mechanical reduction gears are carefully constructed to close tolerances. They have forced lubrication in sprays ahead of the meshing teeth, to the bearings, and to the flexible couplings. Tests have shown that bearings represent at least half the power loss of the entire gear set. Turboelectric drive This type of drive, comprising one or more steam turbine generators and ac propulsion motors, is also used for ship propulsion. It was installed in many United States tankers during World War II because of available manufacturing facilities. The synchronous motors are provided with an induction winding for starting and reversing. Relatively large changes in propeller revolutions are made by alteration of the turbogenerator speed. Motor, generator, exciter, and cooling equipment losses result in several percent lower efficiency than with geared steam turbines. Weights and costs are generally 25-30% higher than for the comparable turbine gear arrangement. Electric drive is not employed unless it offers significant operational or design advantages. These include flexibility of control and the independence of the location of the turbo generator relative to the propeller shaft or propulsion motor
Diesel-electric drive This type of drive, composed of one or more dc diesel generator sets and often a double -ar propulsion motor. is used in tugs, dredges, Coast Guard cutters, and icebreakers, where maneuvering and a wide ange in propeller speed are necessary. For slow-speed operating during maneuvering, the engine speed is often reduced and the generator field excitation is altered to provide wide variation in the motor output and propeller Bridge or pilothouse control of the ship propulsion unit, without action by the engineer on watch, s used with diesel-electric drive and for small, low-powered, direct-drive, and mechanically geared diesel installations. This is the customary arrangement for tugs and dredges Modern practice for large diesel and steamships is to provide pilothouse control of the main engines and no engine-room watch except day workers and when entering and leaving port Propulsion plant monitoring is usually provided in a central control space, with chart recorders or a data storage system. All levels of automation are now being used, from simple manual surveillance of all systems in a fully manned engine space to completely unmanned system recording data and monitoring trends to pinpoint possible trouble Governors Above the operating rpm, ship propeller torque increases faster than engine or turbine torque, and thus ship propeller drive is inherently stable. Because of the ship's pitching, the propeller may lift partially out of the water and the engine may tend to race. To allow for this situation, or for propeller shafting failure. American Bureau of Shipping regulations require that a governor be fitted to limit overspeed to 15% above the rated speed A common type of governor uses oil pressure developed by small pumps incorporated with the main turbine rotors to activate the governor; low lubricating oil pressure will also shut off the steam supply With turboelectric and -electric drive, there is no mechanical connection between the generator set and turbogenerator steam or the amount of fuel injected in the diesel engine cylinder a the propulsion motor and propeller. The operating governor holds generator speed at the set value by throttling (From McGraw-Hill "Encyclopedia of Science and Technology", Vol 8, 1982) Technical Terms 1. marine engine船舶发动机 18.oil- fired燃油的 2. waterborne vessel船,水上运载器 19. marine water-. tube boiler船用水管 3. cruising speed经济航速(民 锅炉 船):巡航速度(军舰) 20. forced draft fan强力通风机 4. steam engine蒸汽机 21. turbogenerator汽轮发电机 5. steam engine汽轮机 casing外壳,箱壳 6. diesel engine柴油机 23. reduction gear减速齿轮/器 7. reciprocating engine往复式发动机 24 nozzle 喷咀,排气管 8. cylinder气(汽)缸 稳定/固定的 9. double- acting双作用 冲动级 0. piston活(柱)塞 27. reaction stage反动级 11.fed- water给水 28. kinetic energy功能 12. condenser冷凝器 oss compound system交叉复合 13. boiler锅炉,蒸汽发生器 系统 14. pressure-confining surface受压面 30. parasitic loss无功/附加损失 15. gearing齿轮装置,传动装置 31. windage loss气体阻力损失 16. rotor转子,电枢 32. gas turbine燃气轮机 otating blade旋转叶片 33. regenerator回热器
Diesel-electric drive This type of drive, composed of one or more dc diesel generator sets and often a double –armature propulsion motor. is used in tugs, dredges ,Coast Guard cutters, and icebreakers, where maneuvering and a wide range in propeller speed are necessary. For slow-speed operating during maneuvering, the engine speed is often reduced and the generator field excitation is altered to provide wide variation in the motor output and propeller speed. Control arrangements Bridge or pilothouse control of the ship propulsion unit, without action by the engineer on watch, s used with diesel-electric drive and for small, low-powered, direct-drive, and mechanically geared diesel installations. This is the customary arrangement for tugs and dredges. Modern practice for large diesel and steamships is to provide pilothouse control of the main engines and no engine-room watch except day workers and when entering and leaving port. Propulsion plant monitoring is usually provided in a central control space, with chart recorders or a data storage system. All levels of automation are now being used, from simple manual surveillance of all systems in a fully manned engine space to a completely unmanned system recording data and monitoring trends to pinpoint possible trouble. Gonernors Above the operating rpm, ship propeller torque increases faster than engine or turbine torque, and thus ship propeller drive is inherently stable. Because of the ship’s pitching, the propeller may lift partially out of the water and the engine may tend to race. To allow for this situation, or for propeller shafting failure. American Bureau of Shipping regulations require that a governor be fitted to limit overspeed to 15% above the rated speed. A common type of governor uses oil pressure developed by small pumps incorporated with the main turbine rotors to activate the governor; low lubricating oil pressure will also shut off the steam supply. With turboelectric and diesel-electric drive, there is no mechanical connection between the generator set and the propulsion motor and propeller. The operating governor holds generator speed at the set value by throttling turbogenerator steam or the amount of fuel injected in the diesel engine cylinders. (From McGraw-Hill “Encyclopedia of Science and Technology”, Vol.8, 1982) Technical Terms 1. marine engine 船舶发动机 2. waterborne vessel 船，水上运载器 3. cruising speed 经济 航速（民 船）；巡航速度（军舰） 4. steam engine 蒸汽机 5. steam engine 汽轮机 6. diesel engine 柴油机 7. reciprocating engine 往复式发动机 8. cylinder 气（汽）缸 9. double-acting 双作用 10. piston 活（柱）塞 11. feed-water 给水 12. condenser 冷凝器 13. boiler 锅炉，蒸汽发生器 14. pressure-confining surface 受压面 15. gearing 齿轮装置，传动装置 16. rotor 转子，电枢 17. rotating blade 旋转叶片 18. oil-fired 燃油的 19. marine water-tube boiler 船用水管 锅炉 20. forced draft fan 强力通风机 21. turbogenerator 汽轮发电机 22. casing 外壳，箱壳 23. reduction gear 减速齿轮/器 24. nozzle 喷咀，排气管 25. stationary 稳定/固定的 26. impulse stage 冲动级 27. reaction stage 反动级 28. kinetic energy 功能 29. cross compound system 交叉复合 系统 30. parasitic loss 无功/附加损失 31. windage loss 气体阻力损失 32. gas turbine 燃气轮机 33. regenerator 回热器
34. aircraft- derived type航空派生型 6. crosshead十字头 笨重机械 57. reverse gear device容器,储器 36. uptake烟道 58. nuclear power核动力 37. destroyer驱逐舰 9. helical teeth斜齿,螺旋齿 38. internal combustion engine内燃机 60. reverse gear device倒车齿轮(传 engine汽油机 动)装置 40. locomotive engine机车发动机 61. electromagnetic电磁的 41. power plant动力装置 62. pneumatic气动的 42. direct driver diesel直接驱动的 63. hydraulic水力的,液压的 柴油机 4. involute渐开线 43. turbo- charger涡轮增压器 65. gear train齿轮组/系 44.two- cycle二冲程 66. meshing teeth啮合齿 45. single-acting单作用的 67. turboelectric drive汽轮机电力 46. moderate-speed diesel中速柴油 驱动 68. synchronous motor同步电动机 47. trunk piston筒形活塞 69. induction winding感应绕组线 48. diesel- electric drive柴油机电力传 70. exciter励磁机,激磁器 49. opposed piston type对置活塞型 71. Coast Guard cutter美国海岸警卫 scavenging扫气,唤气 队快艇 51. crankcase曲拐箱 72. control arrangements控制装置 52. contamination污染 73. governor调速器,调节器 53. piston ring活塞环 74. pilothouse驾驶室冶台 54. crankshaft曲轴 75. racing飞车,超速,空旋 55 connecting rod连杆 76. throttling节流 Additional Terms and expressions 1. propelling engine推进发动机 0. marine pump 船用泵 2. supercharging system增压系统 1l. oil separator分油器,滑油分 3. cylinder scavenging system气缸 换气系统 12. marine boiler船用锅炉 4. fuel system燃油系统 13. refrigerating plant制冷装置 5. lubricating system润滑系统 14. electric power plant电站 6. cooling system冷却系统 15. trouble故障 7. camshaft transmission gear凸轮轴 16. centralized monitoring system巡回 传动机构 检测系统 8. exhaust-gas turbo-charger废气透 17. centralized monitoring system集中 平增压器 监控系统 9. auxiliary machinery辅机
34. aircraft-derived type 航空派生型 35. rugged machine 笨重机械 36. uptake 烟道 37. destroyer 驱逐舰 38. internal combustion engine 内燃机 39. gasoline engine 汽油机 40. locomotive engine 机车发动机 41. power plant 动力装置 42. direct driver diesel 直接驱动的 柴油机 43. turbo-charger 涡轮增压器 44. two-cycle 二冲程 45. single-acting 单作用的 46. moderate-speed diesel 中速柴油 机 47. trunk piston 筒形活塞 48. diesel-electric drive 柴油机电力传 动 49. opposed piston type 对置活塞型 50. scavenging 扫气，唤气 51. crankcase 曲拐箱 52. contamination 污染 53. piston ring 活塞环 54. crankshaft 曲轴 55. connecting rod 连杆 56. crosshead 十字头 57. reverse gear device 容器，储器 58. nuclear power 核动力 59. helical teeth 斜齿，螺旋齿 60. reverse gear device 倒车齿轮（传 动）装置 61. electromagnetic 电磁的 62. pneumatic 气动的 63. hydraulic 水力的，液压的 64. involute 渐开线 65. gear train 齿轮组/系 66. meshing teeth 啮合齿 67. turboelectric drive 汽轮机电力 驱动 68. synchronous motor 同步电动机 69. induction winding 感应绕组/线 圈 70. exciter 励磁机，激磁器 71. Coast Guard cutter 美国海岸警卫 队快艇 72. control arrangements 控制装置 73. governor 调速器，调节器 74. pilothouse 驾驶室/台 75. racing 飞车，超速，空旋 76. throttling 节流 Additional Terms and Expressions 1. propelling engine 推进发动机 2. supercharging system 增压系统 3. cylinder scavenging system 气缸 换气系统 4. fuel system 燃油系统 5. lubricating system 润滑系统 6. cooling system 冷却系统 7. camshaft transmission gear 凸轮轴 传动机构 8. exhaust-gas turbo-charger 废气透 平增压器 9. auxiliary machinery 辅机 10. marine pump 船用泵 11. oil separator 分油器，滑油分 离机 12. marine boiler 船用锅炉 13. refrigerating plant 制冷装置 14. electric power plant 电站 15. trouble 故障 16. centralized monitoring system 巡回 检测系统 17. centralized monitoring system 集中 监控系统
Notes to the text If lower press ratios(final pressure leaving the compressor divided by initial pressure entering)are used, a large amount of heat is available in the exhaust gas which may be covered by heating the compressed air before it enters the combustion chamber 这是一句主从复合句。 If lower pressure ratios are used是条件状语从句;主句是 a large amount of heat is available in the exhaust gas, If which may be recovered by heating the compressed air是定语从句,修饰 a large amount of heat. before it enters the combustion chamber是时间状语从句,修饰前面的 heating,而it是指 the compressed air. 2. However, the direct-driver diesels have a lower fuel oil consumption than do higher-rpI units,and with suitable fuel treatment they will operate on the better grades of the cheaper fuel oil burned in boilers than do higher-rpm units是一个比较状语从句。这里的do即表示 have a low fuel oil consumption burned in boilers是动词过去分词短语,作后置定语,修饰 cheaper fuel oil 3. Lubricating oil consumption of diesel engines is high because of the cylinder-piston lubrication that must be provided and the contamination of the crankcase oil with residues blown by the piston rings 复合介词 because of后面有两个宾语,一个是 the cylinder-piston lubrication,另 个是 the contamination of the crankcase oil o that must be provided是定语从句,修饰the cylinder- piston lubrication with residues blown by the piston rings是说明 the crankcase oil污染 的原因 4. By reversing one or more engines, ready maneuvering including astern operation is provided for by the use of the respective coupling 这是一个简单句。主语为 ready maneuvering,谓语为 is provided for, by the use of the respective coupling和 by reversing one or more engines是介词短语作行为。方式状语。 5. These include flexibility of control and the independence of the location of the turbo generator relative to the propeller shaft or propulsion motor 句中 relative to the propeller shaft or propulsion motor是形容词短语,作后置定语,修饰 6. All levels of automation are now being used from simple manual surveillance of all systems in a fully manned engine space to a completely unmanned system recording data and monitoring trends to pinpoint possible trouble are being used是动词被动态进行式 recording data和 monitoring trends to pinpoint possible trouble均是动词现在分词 短语,作定语用,修饰 a completely unmanned system
Notes to the text 1. If lower press ratios (final pressure leaving the compressor divided by initial pressure entering) are used, a large amount of heat is available in the exhaust gas which may be recovered by heating the compressed air before it enters the combustion chamber 这是一句主从复合句。If lower pressure ratios are used 是条件状语从句；主句是 a large amount of heat is available in the exhaust gas,而 which may be recovered by heating the compressed air 是定语从句，修饰 a large amount of heat. before it enters the combustion chamber 是时间状语从句，修饰前面的 heating，而 it 是指 the compressed air. 2. However, the direct-driver diesels have a lower fuel oil consumption than do higher-rpm units, and with suitable fuel treatment they will operate on the better grades of the cheaper fuel oil burned in boilers. than do higher-rpm units 是一个比较状语从句。这里的 do 即表示 have a low fuel oil consumption. burned in boilers 是动词过去分词短语，作后置定语，修饰 cheaper fuel oil. 3. Lubricating oil consumption of diesel engines is high because of the cylinder-piston lubrication that must be provided and the contamination of the crankcase oil with residues blown by the piston rings. 复合介词 because of 后面有两个宾语，一个是 the cylinder-piston lubrication，另 一个是 the contamination of the crankcase oil。that must be provided 是定语从句，修饰 the cylinder-piston lubrication。with residues blown by the piston rings 是说明 the crankcase oil 污染 的原因。 4. By reversing one or more engines, ready maneuvering, including astern operation, is provided for by the use of the respective coupling. 这是一个简单句。主语为 ready maneuvering，谓语为 is provided for ，by the use of the respective coupling 和 by reversing one or more engines 是介词短语作行为。方式状语。 5．These include flexibility of control and the independence of the location of the turbo generator relative to the propeller shaft or propulsion motor. 句中 relative to the propeller shaft or propulsion motor 是形容词短语，作后置定语，修饰 the independence。 6. All levels of automation are now being used from simple manual surveillance of all systems in a fully manned engine space to a completely unmanned system recording data and monitoring trends to pinpoint possible trouble. are being used 是动词被动态进行式。 recording data 和 monitoring trends to pinpoint possible trouble 均是动词现在分词 短语，作定语用，修饰 a completely unmanned system